Integrated circuits consist of a semiconductor chip containing a large number of transistors and other components housed in a ceramic or plastic case having a large number of leads projecting therefrom. The cases come in a variety of sizes and rectangular shapes, including square, and the number of leads generally varies with the size of the integrated circuit case. Integrated circuits are typically mounted on a printed circuit board either directly or through a socket. Integrated circuits that are mounted directly on a printed circuit board have leads that either project downwardly to extend through holes in the board or are substantially flush with the integrated circuit case and are soldered to mounting pads on the surface of the board. The surface-mounted integrated circuit leads are of two varieties. In one type of integrated circuit known as a plastic leaded chip carrier (PLCC), the leads project horizontally from the sides of the integrated circuit a short distance and then bend downwardly and then under the integrated circuit case. The other type of surface-mounted integrated circuit, known as a "leadless chip carrier (LCC)," utilizes mounting pads that are integrally formed on the underside of the case. In either case, the leads of the integrated circuits rest flushly on the top of printed circuit boards on which they are mounted. Thus, as used herein, the term "leads" includes not only the leads of PLCC integrated circuits, but also the mounting pads of LCC integrated circuits.
Many integrated circuits are mounted on printed circuit boards without prior testing or programming. However, in the event that an integrated circuit is to be tested prior to mounting on a printed circuit board, it must be inserted in a test device. The test device generally contains one or more sockets adapted to receive the integrated circuit. Similarly, some integrated circuits, such as programmable read-only memories and programmable logic arrays, must be inserted in a programming device prior to use. As with the testing devices, programming devices include one or more sockets into which the integrated circuit to be programmed is inserted. The sockets of the testing and programming devices are thus utilized a large number of times.
Conventional integrated circuit sockets used for mounting integrated circuits on a circuit board generally include contacts that are spring-biased against the integrated circuit leads when the integrated circuit is inserted into the socket. These conventional integrated circuit sockets can only undergo a relatively small number of insertion and removal cycles without seriously degrading the performance of the socket. Consequently, conventional testing and programming devices utilize zero insertion force sockets that can be used a large number of times without degradation in their operating performance. These conventional zero insertion force sockets generally include a lever or other mechanism for causing the socket conductors to make contact with the leads of the integrated circuit after the integrated circuit is inserted in the socket. When the integrated circuit is removed from the socket, the lever is actuated to move the socket conductors away from the integrated circuit leads so that the integrated circuit leads do not exert any force on the socket conductors. As a result, the socket can undergo a large number of insertion and removal cycles.
Another problem encountered with conventional testing and programming devices for integrated circuits is the need for a different socket for each of a wide variety of integrated circuits. As mentioned above, different integrated circuits have different sized cases and different numbers of leads. As a result, there must be a separate integrated circuit socket for each type of integrated circuit. This requirement makes conventional testing and programming devices unduly expensive, complex, and difficult to operate.